By changing obesity's status from "a major public health problem" to a chronic disease, Dr. Patrice Harris, a member of the AMA's board of trustees, said that the organization hoped to open up the range of medical interventions that could help the
one-third of Americans now considered obese.

"We believe that raising the level of seriousness by classifying obesity as a disease may encourage third-party payers to increase coverage for treatment and may also encourage greater investment for study," she said.

The decision overrode a recommendation by an AMA committee that had studied the matter for more than a year. While committee members weren't authorized to speak to the media, their final report pointed out that obesity was typically diagnosed using body mass index, a measure that is imprecise and not always associated with poor health outcomes.

For example, someone with a body mass index higher than 30 – the Centers for Disease Control and Prevention's definition of obese – might be perfectly healthy, while someone below that threshold might be sick. Classifying obesity as a disease, the committee argued, might cause confusion because it's difficult to link excess weight to health problems, such as heart disease and type 2 diabetes.

But obesity researcher James O. Hill, executive director of the Anschutz Health and Wellness Center at the University of Colorado, said most professionals who diagnose, treat and research obesity are in agreement that a BMI higher than 30 spells trouble.

"I think it's fair game to argue about what the overweight range of BMIs mean for health because the data is all over the place. But once you're over 30, I think it's pretty clear someone is at risk," Hill said.

Hill said he welcomed the AMA's new classification of obesity.

"We recognize that over a third of the population has a disease. Now we can start getting some standardization for reimbursements and treatments," he said.

Dr. Nikhil Dhurandhar, an obesity researcher at the Pennington Biomedical Research Center in Baton Rouge, La., and vice president of the Obesity Society, said he also believed that the AMA's proclamation was a step in the right direction.

"The recognition of obesity as a disease is an extremely important milestone. Obesity has been a disease. It is now recognized to be so," he said, noting that the society had worked with the AMA on its stance.

Dhurandhar said that while he didn't believe anything the AMA does or says is going to miraculously make obesity disappear, its new position paves the way for more effective diagnosis and treatment.

Dr. Richard Besser, the chief health and medical correspondent for ABC News, said he thought the AMA's declaration was much ado about nothing.

"I think it matters little whether we call obesity a disease, a condition or a disorder. We are already talking about the obesity epidemic. It matters less what we call it than what we do to prevent it," he said.

Besser urged Americans to put more effort into exercising and eating a healthy diet.